Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Quantas disciplinas têm o pinyin shixun?
 ###Tabelas: CREATE TABLE ships_in_class (ships_in_class_id AUTO_INCREMENT PRIMARY KEY, Ship VARCHAR, Hull Number VARCHAR, Laid down VARCHAR, Launched VARCHAR, Commissioned VARCHAR) CREATE TABLE sources_of_income (sources_of_income_id AUTO_INCREMENT PRIMARY KEY, Region VARCHAR, Employment ( salaries & wages) VARCHAR, Self employed VARCHAR, Investment income VARCHAR, Working tax credit VARCHAR, State pensions VARCHAR, Occupational pensions VARCHAR, Disability benefits VARCHAR, Other social security benefits VARCHAR, Other income sources VARCHAR) CREATE TABLE "ca"_or_11th_emergency_flotilla ("ca"_or_11th_emergency_flotilla_id AUTO_INCREMENT PRIMARY KEY, Name VARCHAR, Pennant VARCHAR, Builder VARCHAR, Laid Down VARCHAR, Launched VARCHAR, Commissioned VARCHAR) CREATE TABLE practice_times__&__leaderboard_superbike_senior_tt (practice_times__&__leaderboard_superbike_senior_tt_id AUTO_INCREMENT PRIMARY KEY, Rank INT, Rider VARCHAR, Mon 1 June VARCHAR, Tue 2 June VARCHAR, Wed 3 June VARCHAR, Thurs 4 June VARCHAR, Fri 5 June VARCHAR) CREATE TABLE contents (contents_id AUTO_INCREMENT PRIMARY KEY, Chapter INT, Chinese VARCHAR, Pinyin VARCHAR, Translation VARCHAR, Subject VARCHAR)  
SELECT COUNT Subject FROM contents WHERE Pinyin = Shixun